StructualSubtyping.ts

interface A {
  hoge(str:string): string;
}

interface B {
  hoge(str:string): string;
}

class AImpl implements A {
  hoge(str) {
    return str + "&" + str;
  }
}

var fn = function(b: B) {
  alert(b.hoge("test"));
}

fn(new AImpl());

var aImpl = {
  hoge:(str:string):string => { return "triple:" + str + str + str; }
};
fn(aImpl);